ADHESION PROMOTING COMPOUNDS FOR APOLAR SUBSTRATES

Abstract

Provided in the invention is an adhesion promoter (AP) that is the reaction product of: (i-1) at least one hydroxyl functional (meth)acrylated compound bearing at least two (meth)acryloyl groups, (i-2) optionally, at least one hydroxyl functional (meth)acrylated compound bearing one (meth)acryloyl group (ii), at least one titanium orthoester (ii-a) and/or at least one zirconium orthoester (ii-b), and, (iii) optionally, at least one other compound (iii) that is capable to react with hydroxyl groups. Materials of the invention are suitable for use in coating compositions, inks, paints, varnishes (including overprint varnishes), adhesives (including laminating adhesives), for the making of composites, molding compositions or 3D articles. Materials of the invention are suitable for use in inks and coating compositions (clear or pigmented).

Claims

1. An adhesion promoter (AP) that is the reaction product of: (i-1) at least one hydroxyl functional (meth)acrylated compound bearing at least two (meth)acryloyl groups, (ii) at least one titanium orthoester (ii-a) and/or at least one zirconium orthoester (ii-b), and, (iii) optionally, at least one other compound bearing groups capable to react with hydroxyl groups, said groups being carboxylic acid groups.

2. The adhesion promoter of claim 1 that is further prepared from at least one hydroxyl functional (meth)acrylated compound (i-2) bearing one (meth)acryloyl group.

3. The adhesion promoter of claim 1 wherein the compounds (i-1) have a hydroxyl value (IOH) that is from 10 to 300 mg KOH/g, preferably from 40 to 250 mg KOH/g, and more preferably from 100 to 200 mg KOH/g.

4. The adhesion promoter of claim 1 that is obtained from the reaction of at least one compound (i) as described by Formula 1 with at least one compound (ii) as described by Formula 2: ##STR00005## wherein n>=2 M=Ti or Zr R=alkyl R=alkyl, (poly)ester, (poly)ether (poly)carbonate, (poly)urethane or (poly)amide R=H or CH.sub.3.

5. The adhesion promoter of claim 4, obtained from the reaction of at least 3 equivalents of compounds (i) for one mole of orthoester (ii).

6. The adhesion promoter of claim 1 that is obtained from the reaction of at least one compound (i) as described by Formula 1, with at least one compound (iii) as described by Formula 3 and at least one compound (ii) as described by Formula 2. ##STR00006## wherein m1 R=alkyl, (poly)ester, (poly)ether (poly)carbonate, (poly)urethane or (poly)amide R, R, R, n and M are as described before.

7. The adhesion promoter of claim 6, obtained from the reaction of at least 1 (preferably at least 2) equivalents OH of compounds of Formula 1 and at least 1 (preferably at least 2) equivalents COOH of compounds of Formula 3 with 1 mole of compounds of Formula 2.

8. The adhesion promoter of claim 1 wherein the compound (ii) is an orthotitanate.

9. The adhesion promoter of claim 1 wherein the compound (ii) is an orthozirconate, preferably a zirconium alkoxide and/or a condensed zirconium alkoxide.

10. A radiation curable composition comprising at least 1 wt % of one or more adhesion promoters (AP) of claim 1, and preferably also at least one photo-initiator and preferably the content of Ti or Zr coming from the adhesion promoter (AP) is at least 0.1 wt %.

11. The radiation curable composition of claim 10, further comprising at least one (meth)acrylated compound (UC) that is different from compounds (AP) and preferably further comprising at least one additive selected from the list of: inhibitors, anti-oxidants, UV stabilizers, UV absorbers, dispersing agents, slip aids, fillers, plasticizing agents, flow additives, anti-foaming additives, water scavengers, matting agents, waxes, pigments, dyes, resinous materials dispersed or solubilized in the composition.

12. A process for coating an object or a substrate, comprising the steps of: (a) providing a radiation curable composition according to claim 10, (b) applying said composition onto a surface of the object or the substrate, and (c) irradiating the surface with actinic radiation.

13. A substrate coated with a radiation curable composition according to claim 10, wherein the substrate is a selected from metal, foils, wood, stone, paper, MDF, concrete, plastic, glass, and textile, preferably a non-polar plastic which is corona-treated and/or flame-treated.

14. A packaging material suitable for containing a pharmaceutical, cosmetic, beverage or food grade product comprising: at least one layer formulated from a radiation curable composition according to claim 10.

15. A coating, ink, paint, varnish or an adhesive (such as a laminating adhesive) prepared from an adhesion promoter (AP) or from a radiation curable composition (RCC) of claim 10.

Description

EXAMPLES

[0131] Hydroxyl values (10H in mg KOH/g) were measured using the following potentiometric titration method. This OH Number method covers the automated quantification procedure for hydroxyl groups by means of potentiometric titration. The hydroxyl number is defined as the number of milligrams of potassium hydroxide required to neutralize the hydrolysis product of the fully acetylated derivative prepared out of one gram of resin. Step 1 Acetylation step: All hydroxyl functions are acetylated at 75 C. by acetyl chloride. Step 2 Hydrolysis step: The excess of acetyl chloride is hydrolysed by a solution of N-methyl-2-pyrrolidone (NMP) in water. Step 3 Titration step: The formed acid functions are titrated with KOH 0.5 N solution.

[0132] Acid values (IAc in mg KOH/g) were also measured using potentiometric titration. The total acid number equals the milligrams of potassium hydroxide (KOH) required to neutralize the acid(s) present in 1 g of sample after hydrolysis of present anhydrides. The anhydrides present in the sample are hydrolysed to the corresponding acids during a hydrolysis step and titrated with a standardized solution of KOH. Different titrant solutions i.e. KOH 0.1N and/or KOH 0.5N can be used when analyzing samples with low respectively high total acid number. Potentiometric titration allows end-point identification automatically by means of a titroprocessor and a pH electrode, the manual titration uses a color indicator (phenolphthalein) for visual end-point identification. The amount of KOH is used to calculate the total acid number.

[0133] Viscosity: The viscosity of the adhesion promoters is measured at a fixed shear rate with a cone and plate type rheometer MCR100 (Paar-Physica) according to DIN EN ISO 3219, 25 1/s; 25 C.

[0134] Aspect: The aspect was rated visually.

[0135] Stability: Product stability was tested at 80 C. in 100 ml bottles filled at 90% with cap. Viscosity increase due to polymerization was checked over time.

Synthesis of Compounds (AP) According to the Invention

[0136] A double jacket (oil heated) reactor equipped with an overhead mixer, condenser, thermocouple, and nitrogen inlet is charged with 1 mol of tetraisopropyltitanate (EX 1-3 & Comparative Examples 1, 2 & 4) or 1 mol of tetra n-propylzirconate (EX 4-5 & Comparative Example 3) and different equivalents of oxypropylated/oxyethylated pentaerythritol triacrylate (OH value 98 mg KOH/g; EX 1-5) or TONE M-100 (OH value 161 mg KOH/g, EX 6) or cardura-acrylate (OH value 152 mg KOH/g, EX7). The reaction mixture is heated at 60 C. and isopropanol (EX 1-3 & Comparative Examples 1-4) or n-propanol (EX 4-5) is removed by distillation under vacuum and air sparge. When distillation is completed, the reaction mixture is cooled down at room temperature.

[0137] OH values expressed in mg KOH/g can be converted in milliequivalents OH/g by dividing the value by 56.1 (molecular weight of KOH).

TABLE-US-00001 TABLE 1 Formulation composition and stability EX 1 EX 2 EX 3 EX 4 EX 5 COMP1 COMP2 COMP3 COMP4 Tetra iso- 1 1 1 1 1 1 propyltitanate (mol) Tetra n- 1 1 1 propylzirconate (mol) EO/PO PETIA 5.5 4 3 4 3 (eq OH) Tone M 100 4 (monoacrylate) (eq OH) Carduraacrylate 4 (monoacrylate) (eq OH) HEA 4 4 (monoacrylate) (eq OH) Ti wt % 1.7 2.1 2.6 3.4 9.4 3.2 Zr wt % 3.8 5.1 15.2 Viscosity 463 791 4324 1433 5740 702 Gel Gel 971 @25 C. - mPa .Math. s Aspect colored colored colored colorless colorless colored colored colorless colored Stability OK OK OK OK OK Not Gelification Gelification OK stable on during during storage propanol propanol @80 C. stripping stripping eq: equivalents; COMP: Comparative Example

[0138] In general, compounds (i-1) that bear at least 2 (meth)acryloyl groups are preferred. For instance, stability was less for materials based on COMP 1-3 than for those based on EX 1-5 (Table 1).

[0139] With the above compositions and comparative compositions the following coating formulations were prepared by mixing acrylates, compounds (AP) of the invention and photo-initiators under moderate share.

Adhesion of White Flexo Inks on Plastic

[0140] White flexo inks were prepared from the materials above. Inks were herein prepared in two steps: first a pigment paste is made by mixing (dispersing) TiO2 in an acrylated binder under medium to high shear; in a second step to the pigment paste diluting acrylates, compositions of the present invention and photo-initiator are added. The Table below presents differences in adhesion on plastics. Table 2A presents results for titatanate acrylates (AP). Table 2B presents results for zirconate acrylates (AP). Table 3 provides data related to adhesion on plastic after ageing of the radiation curable composition (a white ink). Table 4 shows adhesion on plastic of clear coats.

TABLE-US-00002 TABLE 2A Adhesion of titanates & speed of curing A1 A2 A3 A4 A5 COMP A1 Formulation Di-trimethylolpropane 25 25 25 25 25 triacrylate Stabilizer solution 1 1 1 1 1 1 White pigment 35 35 35 35 35 35 RDIS (dispersing) 2-Phenoxyethyl Acrylate 19 19 Titanate EX 1 10 29 Titanate EX 2 10 29 54 Titanate COMP4 29 Photoinitiator 10 10 10 10 10 10 blend 12/2 TOTAL 100 100 100 100 100 100 Ti (wt % in 0.2 0.5 0.2 0.6 1.1 0.9 the formulation) Finger touch dry (air) 60 60 100 60 100 30 Graphite (air) 25 25 40 35 25 10 ADHESION immediately 30 m/min 0-24-72 h 5-5-5 5-5-5 5-5-5 5-5-5 5-5-5 3-5-5 60 m/min 0-24-72 h 5-5-5 5-5-5 5-5-5 5-5-5 5-5-5 0-4-5 100 m/min 0-24-72 h 5-5-5 5-5-5 5-5-5 5-5-5 5-5-5 0-1-5

[0141] Photoinitiator blend 12/2 is a mixture of benzophenone (14%), Irgacure 651 (34%), Irgacure 369 (7%), 2-isopropylthioxanthone (13%) and ethyl-4-(dimethylamino)benzoate (32%)

[0142] Stabilizer solution: 4% NPAL in TMPEOTA

[0143] The ink is applied with a K Printing Proofer on corona treated polypropylene (C58 from Innovia) at a film weight of about 2 g/m.sup.2.

[0144] Films were cured under air and at different speed (30 to 100 m/min) with a 140 W/cm mercury lamp.

[0145] Adhesion was measured by tape test using Tesa 4104 tape. The tape is applied on the coating or ink with some pressure to remove air and ensure a close contact between surface and the tape. The tape is pull off with a fast movement. The adhesion is tested just after application, 24 hours and 72 hours after application. Adhesion is expressed from 0 (no adhesion) to 5 (full adhesion).

[0146] UV reactivity was assessed by finger touch the graphite test (the higher the number, the higher the surface reactivity):

[0147] Finger touch: film is assessed as cured (dry) when no tackiness is experienced anymore.

[0148] Graphite test: This test is performed by placing some graphite on the coated surface, followed by rubbing said surface with a piece of cotton. If no black stain remain on the surface, the surface is considered cured. E.g. 10 m/min means that curing at 10 m/min was necessary to pass the graphite test.

[0149] Amount of Ti or Zr (wt %, relative to the total weight of the adhesion promoter): measured by X-Ray Fluorescence spectroscopy.

[0150] Again we see that adhesion promoters prepared from a mono-acrylate (i-2) performed less good than adhesion promoters (AP) according to the invention with a similar Ti contentCOMP A1 versus EX5 (Table 2A).

[0151] Table 2B shows that excellent adhesion was obtained using adhesion promoters (AP) according to the invention, even when the Zr content was low.

TABLE-US-00003 TABLE 2B Adhesion of zirconates & speed of curing Formulation B1 B2 B3 B4 Di-trimethylolpropane triacrylate 25 25 25 25 Stabilizer solution 1 1 1 1 White pigment RDIS (dispersing) 35 35 35 35 Di-trimethylolpropane triacrylate 19 19 Zirconate EX 4 10 29 Zirconate EX 5 10 29 Photoinitiator blend 12/2 10 10 10 10 TOTAL 100 100 100 100 Zr (wt % in the formulation) 0.38 1.11 0.51 1.47 APPLICATION on CORONA treated C58 ADHESION 30 m/min 0-24-72 h 5-5-5 5-5-5 5-5-5 5-5-5 60 m/min 0-24-72 h 5-5-5 5-5-5 5-5-5 5-5-5 100 m/min 0-24-72 h 5-5-5 5-5-5 5-5-5 5-5-5 nt = not tested

[0152] Table 3 shows that white inks can be prepared from adhesion promoters (AP) according to the invention that exhibit excellent adhesion on plastics.

TABLE-US-00004 TABLE 3 Adhesion on plastic after ageing of the liquid ink formulation-white ink Formulation A4 Di-trimethylolpropane triacrylate 25 Stab 12/1 (Additol S120) 1 White pigment RDIS (dispersing) 35 Di-trimethylolpropane triacrylate Titanate EX 2 29 Photoinitiator blend 12/2 10 TOTAL 100 APPLICATION on CORONA treated C58 ADHESION immediately 30 m/min 5-5-5 60 m/min 5-5-5 100 m/min 5-5-5 ADHESION after 3 weeks 30 m/min (0/24/72 h) 0-4-5 60 m/min (0/24/72 h) 0-4-4 100 m/min (0/24/72 h) 0-2-4

[0153] Table 4 below demonstrates that also clear coats prepared from adhesion promoters (AP) according to the invention exhibit excellent adhesion on plastics. To mimic ageing, liquid clear coat compositions were kept for 2 weeks at 40 C. Even then adhesion was better compared to other adhesion promoters available on the market (the simple titanates and zirconates).

Adhesion of Clear Coats on Plastic

[0154] Titanates from EX 2 (formulation B1) perform less good in adhesion after aging at 40 C. for two weeks of the liquid formulation compared to zirconates from EX 4 (formulations B2 and B3). At lower zirconate concentration (formulation B2) adhesion is still excellentas good as when used at higher concentration (formulation B3). Zirconates surprisingly perform better after ageing, even at lower concentrations compared to titanates. They show no discoloration either and hence are highly suited for use in both clear coats and pigmented coat (Table 4).

[0155] Table 4 further shows that a reaction of compounds (i) and (ii) with compounds (iii) gives good results.

[0156] EX 6Compound B: 1 mol of Tetra n-propyl zirconate (30 wt % n-propanol) was reacted with 2 equivalents oxypropylated/oxyethylated pentaerythritol triacrylate (same as used in Example 1) and 2 mol of 2-carboxyethylacrylate; n-propanol was stripped at 80 C. for 3 hours under vacuum. Product has a viscosity of 2320 mPas @25 C. and a zirconium content of 6.0%. Excellent adhesion is obtained in the clear coat (B4).

[0157] Results are presented in Table 4 below:

TABLE-US-00005 Formulation B1 B2 B3 B4 Di-trimethylolpropane triacrylate 61 80 61 80 Titanate EX 2 29 Zirconate EX 4 10 29 Zirconate EX 6 10 Photoinitiator blend 12/2 10 10 10 10 TOTAL 100 100 100 100 Ti (wt % in the formulation) 0.6 Zr (wt % in the formulation) 0.4 1.1 0.6 APPLICATION on CORONA treated C58 ADHESION immediately 30 m/min (0-24-72 h) 5-5-5 5-5-5 5-5-5 5-5-5 60 m/min (0-24-72 h) 5-5-5 5-5-5 5-5-5 5-5-5 100 m/min (0-24-72 h) 5-5-5 5-5-5 5-5-5 5-5-5 ADHESION after 2 weeks at 40 C. 30 m/min (0-24-72 h) 1-4-4 5-5-5 5-5-5 n.t. 60 m/min (0-24-72 h) 0-0-1 5-5-5 5-5-5 n.t. 100 m/min (0-24-72 h) 0-0-3 5-5-5 5-5-5 n.t.

UV Laminating Adhesives

[0158]

TABLE-US-00006 TABLE 5 The product was tested in the following formulations as laminating adhesive for PET/PE. EX1-LA EX2-LA COMPOUND A-EX 4 10 COMPOUND B-EX 6 10 DPHA 65.5 65.5 EBECRYL LEO 10501 24.5 24.5 TPO-L 2 2 Viscosity 25 C. 2000 2010

[0159] Table 6: excellent adhesion are obtained (immediate & after 1 hour) in PET/PE lamination with the combination DPHA and EB LEO 10501 and Zr-acrylates (from Ex 4 and Ex 6 above).

[0160] Polyethyleneterephalate (PET) and polyethylene (PE) films (about 80 microns thickness) were both corona treated. About 5 microns of the coating was applied on the corona treated side of the PET film using an offset Mickle proofer apparatus.

[0161] The corona treated side of the polyethylene film was laminated on the coated PET film. The laminate was cured by UV (LED lamp 8 W/cm.sup.2 air-cooled 365 nm; 1 or 3 times at a belt speed of 5 m/min).

[0162] Adhesion test was assessed by tearing both films from each other (180 C. T peel test). This test was done on two samples, immediately after cure and after 1 hour. A score of 5 means that it was not possible to separate both films, without ripping the laminate. This means that excellent adhesion is achieved with the cured composition of the present invention.

TABLE-US-00007 TABLE 6 Application results EX 1-LA Ex 2-LA Coat weight +/ 5 g/m.sup.2 +/ 5 g/m.sup.2 +/ 5 g/m.sup.2 LED lamp (365 nm) 1 3 1 3 5 m/min 5 m/min 5 m/min 5 m/min Adhesion (0 hrs) 5 5 5 5 Adhesion (1 hour) 5 5 5 5